Glossary

This micronutrient is essential for nitrogen fixation and nitrate reduction.

The dying of plant tissue, usually the result of serious nutrient deficiency or pest attack.

A hydroponic method in which nutrient is fed into grow tubes or trays in a thin film where the roots draw it up. This “nutrient film” allows the roots to have constant contact with the nutrient and the air layer above at the same time.

Also referred to as trace elements, including S, Fe, Mn, B, Mb, An and Cu.

This micronutrient acts as a catalyst in the photosynthesis/respiration process, and is essentialp for the formation of sugars and starches. Iron also activates certain other enzymes.

A portion of a plant stem between nodes.

An instrument for measuring relative humidity in the atmosphere.

A product that destroys or inhibits fungus.

Any of a major group (Fungi) of saprophytic and parasitic spore-producing organisms usually classified as plants that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts. Common fungal diseases that attack plants are “damping-off,” Botrytis, and powdery mildew.

The process of causing the initiation and development of a plant from seed.

To gradually acclimatize a plant to a more harsh environment. A seedling must be hardened-off before planting outdoors.

Chemical substance that controls the growth and development of a plant. Root-inducing hormones help cuttings root.

The offspring from two plants of different breeds, variety or genetic make-up.

Instantly soluble lime, used to raise or lower ph.

One of several brand names/varieties of clay aggregate medium (also known as LECA for light expanded clay aggregate). It is a lightweight, porous substrate with excellent aeration. Because it does not really wick water effectively, Geolite and other LECA mediums are favorites in ebb-and-flow and drip hydroponic systems.

The function of this micronutrient is not well understood, but it is suspected that it might aid carbohydrate transport.

This micronutrient is essential for photosynthesis, where it acts as an enzyme activator during the production of oxygen from water.

The condition of a sick plant with yellowing leaves due to inadequate formation of chlorophyll. Chlorosis is caused by a nutrient deficiency, usually iron or nitrogen; nutrient deficiencies are themselves often caused by a ph that is out of the acceptable range.

A plant produced through asexual reproduction including, but not limited to, cuttings, layering and tissue culture.

To soak new Rockwool in an acidic solution to lower the ph from 8.0 to 5.5.

Leaf tips that turn dark from excess fertilizer and salt burn.

This micronutrient is an internal catalyst and acts as an electron carrier; it is also believed to play a role in nitrogen fixation.

Disease that attacks young seedlings and cuttings, causing stems to rot at the base; overwatering is the main cause of damping-off.

Misting plants with fertilizer solution, which is absorbed by the foliage.